In today's information-intensive environment, information is often electronically transmitted in the normal course of business and other activities. Businesses and individuals want to ensure that these transmissions of proprietary, sensitive, or identity-related information are protected from unauthorized use or theft. One tool that businesses and individuals can use to secure information is a cryptographic technique called encryption. Encryption uses an algorithm to convert information (i.e., plaintext) into a form that is unreadable (i.e., ciphertext) to unauthorized persons. Authorized persons who possess special information, such as a password or key, can convert the unreadable information back to its original form using a decryption algorithm.
Public key-private key cryptography, which makes use of asymmetric key algorithms, is a frequently used encryption technique. In this technique, an encryption algorithm uses a receiver's public key, which is widely available, to encrypt information. A decryption algorithm uses the receiver's private key, which is not available to others, to decrypt the information. The public key and the private key are related mathematically, but the private key cannot feasibly be derived from the public key.
Another encryption technique, called symmetric-key cryptography, makes use of a single secret key, which is shared by a sender and a receiver. The secret key is used by encryption and decryption algorithms to both encrypt and decrypt information. Unlike public key-private key cryptography, symmetric-key cryptographic techniques require the sender and the receiver to securely share the secret key in advance. To ensure security of the secret key, the sender and receiver share the secret key separately from the transmission of the encrypted information.
Regardless of which encryption technique is used, encryption transforms information in an entire electronic file so that all of information in the encrypted electronic file is rendered unreadable. The encrypted electronic file is transmitted from a sender to a receiver and the receiver uses an appropriate key to decrypt the electronic file and render the information readable. Consequently, an entity that intercepts or inadvertently receives the encrypted file will be unable to read any of the information that is contained in the file without the appropriate key.
Encrypting all of the information in an electronic file is sometimes not necessary and, in certain circumstances, it may even be desirable to have some of the information remain readable. For example, it may be desirable to transmit a document such that certain information (e.g., a name) remains readable while maintaining secret other sensitive information in the document (e.g., a social security number (SSN), bank account number, etc.). However, as discussed above, conventional encryption techniques render all of the information in an encrypted electronic file unreadable. Therefore, there is a need for improved systems and methods that provide alternatives to conventional encryption techniques.